Instrument Hook Up Drawing

Instrument Installation or Hook-up CONTENTS 

Introduction 

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Hook-up drawing for Pressure/Differential pressure measurement instruments 

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Hook-up drawing for Flow measurement instruments 

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Hook-up drawing for Temperature measurement instruments  instr uments 

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Hook-up drawing for Level measurement instruments  -

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Impulse Pipe and Tube 

Introduction

What What is Inst Instru rume ment nt hook hook-u -up p draw drawin ing?  g?  Instrument hook-up drawing gives the detail of the connection from the tapping point int in the the process cess line ine up to the the sensin nsing g instr strum ume ent. So, while Piping and Instrumentation Diagram (P&ID) shows the instruments that are to be connected to a process line, the Instrument Hook-up gives detail info nformati ation about how tha that is to be done one durin ring actu ctual ins instal tallati latio on.

Why do we need Instrument Hook-up drawing?  - To make measurements accurate accurate and reliable - To make measurement measurement systems systems safe - To be used at site for correct instrument erection & installation

Introduction: How does a typical hook-up drawing look like? Type Type of inst instru rume ment nt

Scop cope of work work

Bill Bill of Mate Materia riall

Accessories Tapping Tapping orientation orientation

Impuls Impulse e line

Sensing Sensing instrument/t instrument/transm ransmitter itter with valve valve manifolds manifolds

Fittings

S

Introduction: Engineering Process & Interface Input documents required for making Instrument Hook-up drawings:  

Contract Requirement and Project Design Criteria  Piping and Instrument Diagrams (P&ID)  Instrument List (with Instrument Datasheet)  Piping Material Classification (PMC) or Piping Material Specification (PMS)  Instrument Rack grouping, elevation of tapping and rack Valve List (for (f or Instrument Air)  Control Valve  Tank and Heat Exchanger GA drawings Output documents from Hook-up drawing:  Bill

of Material (erection and installation)

Support drawings along with Hook-up drawing:  

Pipe Support drawing  Piping Isometric Drawing General check-points:  

Check Instrument Installation material specification with Boiler/Turbine group group for maintaining uniformity across plant.  Instrument/Rack location and drain connections to be informed to related departments for proper end connections.  Elevation of rack provides enough scope for requisite slope for instrument mounting.  Cross-check the connections of materials at interface points.

Hook-up drawing for Pressure/Differential Pressure/Differential pressure measurement instruments a)

Tapping points -  Prefe Preferre rred d angl angle e of tapp tappin ing g poin pointt in hori horizo zont ntal al line line::

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Gas Gas serv servic ice: e: with within in 45 degre degree e arou around nd verti vertica call cent centre re-l -lin ine e Stea Steam m serv servic ice: e: with within in 45 degr degree ee arou around nd hori horizo zont ntal al cent centre re-l -lin ine e Liqu Liquid id serv servic ice: e: with within in 45 degr degree ee of hori horizo zont ntal al cent centre re-l -lin ine e in lowe lowerr half half,, pref prefer erre red d hori horizo zont ntal al beca becaus use e taps taps below elow the the cen centre tre-li -line can can accu ccumula mulate te soli olids, ds, whil hile tap taps abov bove the the cen centretre-lline can accu ccumul mulate air or non-cond non-condensi ensing ng gases. gases. For For diffe differe rent ntia iall pres pressu sure re meas measur urem emen ent, t, both both tapp tappin ing g poin points ts shou should ld be at same same elev elevat atio ion. n.

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For gas service

For steam service

b) Root valve   - Root Root (iso (isola lati tion on or bloc block) k) valv valves es are are requ requir ired ed to sepa separa rate te the the enti entire re meas measur urem emen entt syst system em from from the the main main pipe pipeliline ne when when nece necess ssar ary, y, but but they they shou should ld not not affec affectt the the pres pressu sure re sign signal al..

For liquid service

- Root oot valv alves are to be locate cated d as close lose as poss ossibl ible to tap tap con connecti ection ons. s. - Root Root valv valves es shal shalll be desi design gned ed for for maxi maximu mum m desi design gn pres pressu sure re and and temp temper erat atur ure e of the the pipi piping ng syst system em - For For pro proces cess pre pressu ssure grea greate terr than than 40 bar( bar(g) g) (or (or as spe specifi cified ed in cont contra ract ct), ), two two nos. nos. of roo root valves to be used used.. Root valves

c) Pref Prefer erre red d Loca Locatio tion n of meas measur urin ing g inst instru rume ment nt (sec (secon onda dary ry)) with with resp respec ectt to proc proces ess s tappi tapping ng (pri (prima mary ry)) 

Gas Gas serv servic ice e - seco second ndar ary y abov above e prim primar ary y

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Liqui Liquid d servi servicece- second secondary ary below below primar primary y

Lesson learnt (Root valve): To provide accessibility, Root valves were brought to floor level whi which caused a potential safety issue (high steam application) and slope issues whi which could lead lead to inac inaccu cura rate te meas measur urem emen ent. t. The The valv valve e was was mov moved near near to tapp tappin ing g poin point. t.

For gas service, secondary above primary

Hook-up drawing for Pressure/Differential Pressure/Differential pressure measurement instruments d) Impu Impuls lse e tube/ tube/pi pipe pe and and fittin fittings  gs  

The The requ requir ired ed diam diame eter ter of the the impu impuls lse e line line depe depend nds s on the the serv servic ice e cond condit itio ions ns.. Inte Intern rnal al diam diame eter ter of tube tube/p /pip ipe e shou should ld be adeq adequa uate te to allo allow w gas bubbles to flo flow up and out of a liquid system tem, and to allow liquid drops to flo flow down (ISO ISO 2186:20 :2007 does not allow diameter ter less than than 6mm, 6mm, pref prefer ers s 10mm 10mm and and spec specif ifie ies s a maxi maximu mum m of 25mm 25mm). ).

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It is always recommended that the shortest possible impulse-line lengths be used. The diameter is given as per the length for the impu impuls lse e as per per the the serv servic ice e in ISO ISO 2186 2186:2 :200 007, 7, Tabl Table e A.1 A.1

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Mate Materi rial al of Impu Impuls lse e line line shou should ld be as per per serv servic ice, e, proc proces ess s cond condit itio ions ns..

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Wall Wall thic thickn knes ess s of impu impuls lse e line line to be as per per ANSI ANSI B31. B31.1 1 for for a give given n temp temper erat atur ure e and and pres pressu sure re rati rating ng..

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Fit Fittin ting mate materi ria al shoul hould d con confor form to ANSI B16. B16.11 11 and and sho should matc match h with the the impul mpulse se line mate materi rial al (for for e.g. .g. SS fitt fittiings ngs for for SS tub tubing) ng). An exception to thi this is brass fit fittin tings with copper tubing. Diffe fferent materi teria als could cause Galvanic corrosion due to differ ferent electrod rode po en en a s o ss m ar me m e a s. s.

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For For gas gas appl applic ica ation tion:: slope fro from proc rocess line to measuring instrum rument to be upwards rds with gradient of minimum 8% for for self-dr -draining (oth (other erwi wise se lowlow-po poin intt drai drain n to be prov provid ided ed)) For For stea steam m: slope for for impulse line to be downwards from rom tap tapping point to measuring instrum rument, with gradient of minimum 8% for for selfvent ventin ing g of nonnon-co cond nden ensi sing ng gase gases s (oth (other erwi wise se high high-p -poi oint nt vent vent to be prov provid ided ed)) For For liquid liquid:: dow downwar nwards ds slop slope e of mini minimu mum m 8% (oth (other erw wise ise high high-p -poi oint nt vent vent to be prov provid ided ed))

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Lesson learnt: In case of tube fittings, compression fittings (double ferrule type) for pressure greater than 40 bar (g) caused leakage. To To correct, welded fittings were w ere used for all high pressure application.

Hook-up drawing for Pressure/Differential Pressure/Differential pressure measurement instruments Accessories:  a)

Instrument Isolation Valve and Valve manifolds :  Valv Valves es/v /val alve ve mani manifo fold lds s are are inst instal alle led d to perm permit it oper operat atio ion, n, cali calibr brat atio ion n and and trou troubl bles esho hoot otin ing g of the the seco second ndar ary y devi device ce (mea (measu suri ring ng inst instru rume ment nt)) with withou outt remo removi ving ng it. it. An asse assemb mbly ly of two, two, thre three e, or more more valv valves es,, often ften in one one pack packag age, e, used used to faci facili lita tate te cali calibr brat atio ion n and and main mainte tena nanc nce e is call called ed valv valve e mani manifo fold ld.. Thes These e valv valves es are are used used to: to:

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Isol Isolat ate e the the seco second ndar ary y devi device ce from from the the impu impuls lse e line lines s Open a path betwe tween the the high and low pressure sides of the secondary device. The The secondary device zero (no flo flow signa gnal) can be adju adjust sted ed at oper operat atin ing g pres pressu sure re with ith one one bloc block k valv valve e clos closed ed and and the the bypa bypass ss valv valve( e(s) s) open open Drai Drain n or vent vent the the seco second ndar ary y devi device ce and/ and/or or the the impu impuls lse e pipi piping ng to the the drai drain n or to atmo atmosp sphe here re..

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2-valve manifold: One valve connects the process to secondary instrument, another valve allows testing, t esting, venting and calibration (when the first valve is closed). between the high and low 3-valve manifold: Two block valves provide instrument isolation, and one equalize valve is positioned between transmitter process connections. connections. Equalizing valve provides a means to check for f or 0 PSI differential diff erential pressure when when both Isolation valves are closed and only equalizing valve is left open. Such valves are used for d/p type measurement. 5-valve manifold: Two block valves provide instrument isolation and one equalize valve is positioned between the high and low transmitter process connections. In addition, two drain/vent valves allow for venting/draining, and in-process calibration capability.

2-valve manifold

3-valve manifold

5-valve manifold

Hook-up drawing for Pressure/Differential Pressure/Differential pressure measurement instruments Accessories:   ) Remote Seal:  b  This This arra arrang ngem emen entt of an Remo Remote te Isol Isolat atin ing g diap diaphr hrag agm m at the the tapp tappin ing g poin pointt and and a capi capillllar ary y tube tube cont contai aini ning ng a fill-fluid wh fill-fluid whic ich h comb combin ine e to tran transfe sferr the the pres pressu sure re from from the the proc proces ess s to the the meas measur urin ing g inst instru rume ment nt with withou outt allo allowi wing ng the proc proces ess s fluid fluid to come come dire direct ctly ly in cont contac actt with with the the seco second ndar ary y inst instru rume ment nt is call called ed Remo Remote te Seal Seal.. This This is empl employ oyed ed when when,, Ther There e is a need need to prot protec ectt tran transm smit itte terr sens sensor or from from hars harsh h proc proces ess s flui fluid d  Process fluid is viscous or might get frozen in the impulse tube because of  temperatu temperature re fall Proc Proces ess s flui fluid d migh mightt clog clog the the impu impuls lse e line line with with cont contam amin inan ants ts  Process fluid is to be prevented from getting contaminated (as in food  rocessin s stems

c) Cond Conden ensa sate te Pots Pots (Sea (Seall Pots Pots or Rese Reserv rvoir oirs) s):  :  To meas measur ure e the the pres pressu sure re of high high-t -tem empe pera ratu ture re steam steam with withou outt dama damagi ging ng the the pres pressu sure re trans transmi mitte tterr sens sensor or,, Cond Conden ensa sate te Pot Pot is used used whic which h has has a smal smalll volu volume me of liqu liquid id which hich crea create tes s a barr barrie ierr for for stea steam m which hich prev preven ents ts it from from reac reachi hing ng the the sensing sensing element. element. Pigt Pigta ail Sip Siphon hon: It is a loop of tub tube which hich serv serves es the the same same purp urpose ose as the the con condens densat ate e pot. pot. The The cond conden ense sed d stea steam m will ill accu accumu mula late te and and crea create te a barr barrie ierr for for stea steam. m.

Condensate pot

Hook-up drawing for Flow measurement instruments By measuring differential-pressur diff erential-pressure e (e.g. Orifice, nozzle)

Flow measurement (on the basis of installation type)

By In-line Mechanical or Electrical flow meters (e.g. Positive Displacement meter, Ultrasonic meter)

In situations where the flow measurement is done by measuring differential pressure, all sections of Diff erential Pressure measurement measurement are to be followed.

Magnetic flow meter:  The magnetic flow meter must be electrically grounded to the process liquid. This is because the magnetic meter is part of the path for any stray st ray current traveling traveling down the pipeline or through the process liquid. Bonding, by grounding the meter at both ends to the process fluid, provides a short short circui circuitt for stra curren currents ts routin routin them them around around the flowflow-tub tube e instea instead d of throu throu h it. If the s stem stem is not not ro erl rounde rounded d these these curren currents ts can create a zero shift in tthe he magnetic flow meter output.

Grounding when pipe is conductive

Grounding when pipe is non-conductive

Hook-up drawing for Temperature measurement instruments 

Connection type of the thermo-well: flanged, weld, threaded etc should be indicated as per the instrument selected.

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Thermo-well drawing drawing to be reviewed with respect r espect to Isometric drawing to avoid thermowell diameter mismatch.

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ASME PTC 19.3 2010 does not recommend velocity velocity collar as a rigid support for the purposes of shortening the unsupported length.

Hook-up drawing drawing for Level measurement instruments         

In case of Level measurement by D/P method, all the points of Differential Pressure measurement apply as it is. In DP type Level Measurement for avoiding density variation in one Leg Wet leg Calibration is performed Root valve and impulse impulse pipe shall have a minimum minimum of 1” (DN 25 mm) diameter From Tank tapping tapping point to stand stand pipe and further from stand pipe tapping tapping to instrument instrument Impulse routing shall be always straight with minimum bends. For Displacer type Level transmitter, side-side side-side and side-bottom criteria should be checked with instrument selected. For Tanks Level Gage, center-to-center (C-C) distance should be checked with application requirement. For a Tank multiple Level Level Gauges can be used used with overlapping overlapping C-C C-C length. For Ultrasonic Ultrasonic and Radar Type Level Transmitters Signal transmission angle to be checked checked of nozzle. nozzle.

GL: Gauge length SL: Sigh length (Visible length) ME: Center-to-center (C-C) distance

Hook-up drawing for Instrument Air supply 

This hook-up contains the connection from the instrument air source to the instrument requiring the air for its working.

 Air

line tube material (Copper/SS), size and thickness to be considered as per requirement

Impulse Pipe and Tube Pipe and Tube, both are hollow structures designed to provide an enclosed pathway for fluids to flow.

Connector: tube Connector: tube fitting designed to connect tube to pipe.

manuf actured with with  Essential difference is that both are manufactured different standards. 

Pipes are thick-walled, tubes are thin-walled.

fitt ing is a  Tube is never threaded (like a pipe) and a tube fitting must to join ends. 

Tube is specified by OD (Outer diameter) and wall thickness.

Pipe

is denoted by NB (Nominal bore) or NPS (Nominal inches] or DN (translated DN (translated to Nominal Pipe Size) [both in inches] mm] and Schedule (wall thickness). NB, NPS Diameter) [in mm] or NB are equivalent in their meaning, but different in dimensions used.

Union : tube fitting designed to connect tube to tube. If union joins tubes of different sizes, it is called reducing union. To connect two pipes, Coupling is used. Bulkhead fittings: Connectors and fittings designed to fit f it through holes drilled in panels or enclosures. Similar to Connectors and Union except long length of central ‘barrel’ piece and a nut to lock the piece into the place.

NPS

(or DN or NB) are closely related to internal diameter but are not exactly same as the internal diameter.

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Elbow : Fittings with a bend

For a given NPS, OD gets fixed. As the Schedule changes the wall thickness increases (thereby changing the Internal Diameter). Tee fittings: Fittings that

Impulse Pipe and Tube: Connection types Considering hook-up, pipes are connected to another pipe or a component by:  Socket

weld

Threaded connection Flanged connection

Tubes are connected to other tubes or a component by:  

Socket weld  Compression fittings 

Tubes are too weak to support threads t hreads or flanges.

Socket The left end is Socket end in which a tube is inserted and welded at the joint. The right end is threaded for Pipe connection as it is a male connector.

Thank You